Now is the time for the Lords to earn its ermine. There are few occasions when its lack of democratic legitimacy is an advantage - but the communications bill is one. Over the next weeks, the Lords can exercise its duty to protect the citizens against the shabbier venalities of democracy. (Though that may not be what Tony Blair meant when he chose to leave them 100% unelected).

With both Labour and Conservative leaders in humiliating thrall to the menacing might of Rupert Murdoch, this is the legitimate time for the unelected Lords to rebel against the elected Commons and stop Murdoch seizing yet another slab of the British media.

Yesterday saw the opening skirmishes over the communications bill: the Lords will vote on it in a few weeks. This vast and baggy bill, packed with important but uncontentious technicalities, contains two momentous threats to the future quality of broadcasting. The key clauses have one sole function - to remove all obstacles to Murdoch seizing Channel 5, overshadowing ITV and, within a short time, providing the main competition to the BBC. The bill abolishes the requirement for owners of TV companies to be British or EU citizens. (Murdoch took US nationality to take over Fox TV: the US bans foreign ownership.)

The other crucial clause removes existing laws that prohibit anyone who owns 20% or more of newspaper readership from buying into TV. Murdoch already owns over 40% of Britain's newspaper readership, as well as his mighty Sky satellite empire.

Pity the wretched ministers charged with pushing through this shameless bill, Downing Street's gun at their heads. Three hapless women - Tessa Jowell at the Department of Culture, Media and Sport, together with Patricia Hewitt at the Department of Trade and Industry and Tessa Blackstone leading in the Lords - all look miserable and sound less convincing every time they speak.

It's hard to find a soul in the Labour party who supports this: even those paid to mouth assent look ashamed. However, politics is a savage game and one-day-wonder resignations rarely change anything beyond the career path of resigners. To steal a line - the political grave is a fine and private place, but none from there their steps retrace. Besides, there are too few good senior women to see these three walk the plank.

A fourth woman, former cabinet minister Margaret Jay, probably spoke for all in condemning this shocker yesterday. But the unhappy tones of Ms Jowell on the Today programme was a cringe-maker: "This is not about Rupert Murdoch. Let's be absolutely clear, these proposals are proprietor-neutral."

Where did these killer clauses come from? Chris Smith's white paper did not contain them: they were not on his radar screen, he says. Trying to hide the blindingly obvious reason why, Downing Street has produced bizarre excuses. The call of the wild free market is invoked. There is indeed a need for untrammelled innovation in the white heat of the deadly competitive international phone/IT market. But they deliberately mix that in with the quite different question of who owns and controls broadcasting. The call to free up TV to exhilarate investment from America defies belief: welcome to AOL Time Warner and Disney. As the EU struggles to save cultural goods from the terms of GATT so countries can protect their cultural industries from US depredation, Britain throws open TV to America, without any reciprocity. US owners can offload backlists of old US programmes - easy profits even if viewer numbers fall.

But worst is the clause letting Murdoch buy Channel 5. Pretending C5 needs investment is absurd: its principal shareholder is five times the size of Granada and Carlton put together. But to Murdoch it would be invaluable. He could buy up sports rights for both terrestrial and satellite, outbidding all-comers, cross-promoting across his newspapers and two TV platforms. With Murdoch behind it, Channel 5 could destroy ITV as it is unshackled by ITV's public service obligations. That would bring it head to head with the BBC. Optimists say naively that the BBC would shine with no competition but bilge. But the BBC is always dragged down by the surrounding media ecology, even if it keeps its nose just above the prevailing water level. Now is a low ebb to praise British broadcasting: what was once one of the best in the world is now only one of the least worst. Greg Dyke's belated promise this week that the BBC will do better still doesn't sound as if he understands how radical a revolution is needed. God knows how many thousands of hours went into producing their latest self-laudatory nonsense "Vision, Mission, Values", but it only emphasised the current chasm between rhetoric and output.

But however bad, you can bet Murdoch's arrival would make it worse. All he touches turns to dross - and gold in his own pocket. Date the decline of Britain's press into a laughing stock among European countries from the day he bought the Sun, and Mrs Thatcher let him break all media laws to acquire the rest. Mrs Thatcher twisted EU law to get him an exemption when he launched Sky to allow him to use almost entirely US programming, breaking EU import quotas. In 1996, John Major, desperate to assuage the wrath of his press, gave him all he wanted in the new digital universe. (Labour put up no objection, with Geoff Hoon smoothing its path through the Commons.) Now here we go again, Tony Blair handing over the last prize to Murdoch, whose papers repay him handsomely just now. (But only for now, so long as there is no euro referendum.) Murdoch is the great corrupter of politicians: John Major dates his downfall from the day Murdoch decided to oust him. Politicians fear they need this bully's patronage. Whenever they cave in, his grip on politics tightens.

Now it is down to the Lords to fight off this threat: "I hope their lordships will be conscious of their responsibilities," says Chris Smith, who wants the landmines inserted into his bill removed. At least Labour rebel peers, led by Lord Puttnam, will know they rebel with the wholehearted support of virtually all their elected counterparts in the Commons. The same is true of the Tories: Iain Duncan Smith missed a magnificent chance to seize the moral high ground and put Labour to shame over this - but no doubt he was well warned that Murdoch's daisycutters (tabloid and broadsheet) would fall upon his unprotected pate. Tory peers may consider that if Conservatism means anything, its values surely include conserving the best of British broadcasting.

Now here is a theory I would like to believe: Labour hierarchs would not be heartbroken to lose these clauses in the Lords. No 10 can tell Mr M that they tried, but the damned Lords just wouldn't wear it and now the time has run out. Did our best, not our fault, awfully sorry, so please don't beat up on us, please.